Development of superparaelectric BaTiO₃ system ceramics through heterovalent Mn-Nb co-doping for DC-bias free dielectrics

Abstract

BaTi(1-2x)MnxNbxO3 ceramics with 0 ≤ x ≤ 0.10 were fabricated and the crystal structure, microstructure, dielectric, and ferroelectric properties were investigated. The samples with x ≥ 0.06 showed a pseudo-cubic symmetry in a wide temperature range of -150 oC to 200 oC but exhibited domain structures and a slightly slanted polarization-electric field response. The dielectric constant for these samples exhibited a comparatively flat response with temperature. The DC-bias dependence of the dielectric constant improved drastically from the samples with x = 0.06. A qualitative model of chemical grain size (CGS), defined by the distance between the co-dopant ions, was proposed which expressed the phonon propagation length in a wide temperature range and thus induced superparaelectricity in the ceramics. A critical CGS = 810 pm was determined geometrically for the sample with x = 0.06 such that samples with x ≥ 0.06 were superparaelectric in nature.

Grain size-independent dielectric and ferroelectric properties of superparaelectric Mn–Nb co-doped barium titanate ceramics

“…The unique feature of spontaneous polarization in BT has attracted researchers from diverse fields such as ferroelectricity, piezoelectricity, photovoltaics, etc. [1][2][3][4][5][6] For instance, the spontaneous polarization leads to a higher dielectric constant in BT ceramics because of which BTbased ceramics are important dielectric components of multilayer ceramic capacitors (MLCCs). 7) With the advancement in technology, the dielectric materials used in MLCCs are rigorously investigated to fulfill the demands of future applications.…”

“…[8][9][10] However, the dielectric constant of BT exhibits strong temperature dependence and DC-bias dependence (Δε/ε 0 ) due to its ferroelectric nature. [1][2][3] Moreover, an increase in the volumetric efficiency of MLCCs would require decreased dielectric layer thickness with ceramics exhibiting a submicrometer grain size. 7) However, the dielectric and ferroelectric properties (hereafter written as "electrical properties") of BT ceramics firmly depend on the grain size (GS), known as the "size effect."…”

“…Recently, Sapkota et al proposed a concept of chemical grain size (CGS) to develop a superparaelectric BT system ceramics, BaTi (1-2x) Mn (x) Nb (x) O 3 , and reported good DC-bias free properties. 3) In this concept, the phonon propagation length was expressed by the CGS, which was determined by the separation of the co-dopant ions. 3) The ceramics with x ⩾ 0.06 (CGS ⩽ 810 pm) were reported to be superparaelectric because they did not exhibit a phase transition temperature (T c ) from −150 °C to 200 °C but showed S-shaped polarizationelectric field (P-E) responses.…”

“…3) In this concept, the phonon propagation length was expressed by the CGS, which was determined by the separation of the co-dopant ions. 3) The ceramics with x ⩾ 0.06 (CGS ⩽ 810 pm) were reported to be superparaelectric because they did not exhibit a phase transition temperature (T c ) from −150 °C to 200 °C but showed S-shaped polarizationelectric field (P-E) responses. 3) However, the ceramics with x ⩽ 0.05 (CGS ⩾ 860 pm) exhibited a T c in the temperature profile and were reported to be non-superparaelectric.…”

“…3) The ceramics with x ⩾ 0.06 (CGS ⩽ 810 pm) were reported to be superparaelectric because they did not exhibit a phase transition temperature (T c ) from −150 °C to 200 °C but showed S-shaped polarizationelectric field (P-E) responses. 3) However, the ceramics with x ⩽ 0.05 (CGS ⩾ 860 pm) exhibited a T c in the temperature profile and were reported to be non-superparaelectric. 3) The reason behind such a significant change in the phase transition behavior, although the difference in the values of the CGS was small, was the competing long-range force (LRF) and shortrange force (SRF).…”